Method and means fob protecting



G. s. QUINN 2,454,745 METHOD AND MEANS FOR PROTECTING FLUORESCENT COATINGS AND THE LIKE Filed Jan. :5, 1946.

Nov. 23, 1948.

' m 'rmwm I INVENTOR Gerald 3. Quinn ATTORNEY maul Nov. :3, i948 .METHOD AND MEAN rwonasosn'r 8 FOR PROTECTING COATINGS AND THE Gerald s. Quinn, Salem, Mas... minor to Sylvanla Electric Produc ts Inc.,

Salem, Mass., in

corporation of Massachusetts Application January 3, 1946, Serial No. 638,747

. 6 Claims.- v.(ci. 316-17) 7 This invention relates -to means and-method for protecting fluorescent or other types of coatlugs for lamps or'other electronic devices prior to the final exhausting, gassing and sealing oil operations.

- lnthemanufacture of electronicdevices having such coatings it is highly desirable to exhaust and seal the envelope thereof before an extended elapse of time subsequent to the application and processing of the coating. If the finished coating is subjected to prolonged exposure to an oxidizing or impure atmosphere its efliciency is impaired.

It is an object of the present invention to protect the coating from deterioration when it becomes necessary or desirable to delay the final exhaustion and sealing of the device.

A further object of the invention is to provide means to protect the device from excessive internal' pressure when it is subjected to heat.

Other objects and features of the invention will more fully appear from the following description taken in connection with the accompanying drawings and will be particularly pointed out in the claims.

I flow of'alr into the envelopesince when the pressure within becomes reduced to a safe degree the natural flow of the glass while still hot automati- .cally reseals the envelope. The fluorescent'coating is thereby completely, protected from contaminating atmosphere throughout the manufacture The invention applies particularly to electronic devices having a fluorescent or other coating and which require that time consuming operations be performed thereon after the coating has been applied and before its envelope is finally sealed off. To protect the coating from deterioration during this intervening period an inert gas is intro- .duced into the envelope and the air therein flushed out, pumped out, or otherwise removed.

The envelope is then temporarily sealed off.

The invention further provides that a relatively high heat may be applied to the lamp after being temporarily sealed off without causing rupture of the envelope due to excessive pressure developed by the heated gas within. Pressure relief means are provided in the form of a seal at the end of the envelope exhaust tube. The seal is composed of glass of low softening point. The softening point of the glass seal being of such a value that it will soften before the glass of the envelope and in so doing will permit harmful pressure developed in the envelope to "be vented through the exhaust tube. Moreover, the glass seal also acts as a check valve to prevent a reverse of the lamp or other device.

To provide a better understanding of the invention a specific embodiment thereof'will now be described and illustrated in which:

Fig. 1 is a general view of a fluorescent lamp tube of circular form after its inner wall has been coated with a fluorescent coating.

Fig. 2 illustrates the lamp tube together with means for introducing a protective-gaseous atmosphere into the envelope.

v Fig. 3 is an enlarged detail sectional view 01' the base portions of the lamp illustrating the manner in which the lamp is temporarily sealed 0153.

Fig. 4 illustrates somewhat diagrammatically an oven containing a lamp upon which a straightenlng operation is being performed.

Figs. 5 and 6 illustrate the manner in which a velope with at least a portion of its inner wallcoated with fluorescent material or having a coated element therein susceptible to contamination.

The lamp illustrated when completed is of circular form and its tubular envelope I lies substantially in a plane.

To facilitate its manufacture, however, the lamp tube is first given a circular outline and a slightly spiral convolution thus disposing its ends 2 in offset relation to permit fabricating operations such as the fusing of stem members upon the lamp tube;

Fig. '1 of the drawings illustrates 'a-lamp tube partially insection to show its fluorescent coating 3. The coating is applied and baked to remove all solvents and binder material in the conventional manner and upon completion of the coating the ends of the tube are closed by fusing thereto the stem members 4. The stem members are provided respectively with exhaust tubes 5 and i.

the drawings in In the conventional manner of manufacturing tubular lamps the flnal steps in their manufacture are carried out in fairly rapid succession after the fluorescent coating is applied and treated. In the present invention, However. the coating is protected from contamination by contact with impure or oxidizing atmospheres during an intervening period of time after the coating is applied and before final sealing oil of the lamp.

A desirable means for protecting the coating is to introduce an inert gas to replace the air withthe desired condition within the lamp has been obtained both exhaust tubes are sealed oil thus protecting the coating indefinitely.

The inert atmosphere may be introduced in any desired manner for example, a single exhaust tube may be used in which case the air in the envelope is removed by a pump and inert gas introduced thereafter through the same tube.

A further feature of the invention is to protect a the lamp from excessive internal gas pressure when it is subjected to the application of heat. In the production of the type of lamp described herein the spiral configuration of the tube must be flattened to provide a practical lamp and such operation must be executed after the application of the fluorescent coating.

This operation requires that the lamp be heated suiiiciently to permit the tube to be bent until it lies substantially in a flat plane. It will also be noted that the straightening operation is performed after the protective inert gas has been sealed into the lamp.

To execute the straightening operation the lamp is desirably placed in an oven i wherein its temperature is raised to the point where the glass .becomes slightly plastic. A weight Ii is placed upon the high end of the tube and its other end is preferably lightly clamped as shown in Fig. 4. The action of the weight gradually bends the tube until it lies in a flat plane upon the support l2 within the oven.

During the straightening operation the gas sealed within the lamp is heated and greatly increases the pressure therein which tends to expand and distort the lamp. To prevent this possibility a relief and check valve device is provided to relieve excessive pressure within the lamp. The

desired result is achieved by constructing the outer portion I} of one of the exhaust tubes for example, the tube 5 of soft glass or similar material having a melting point lower than that of the material of the lamp itself. Desirably a short section it of soft glass tubing'or a head is used to seal off the tube 5.

The high temperature of the oven causes the soft glass to become more plastic than-the lamp itself. Consequently the increased pressure within the lamp forces an opening in the exhaust tube 5 as shown in Fig. 5 thus relieving the excessive pressure.

-When the pressure becomes normalized the plasticity of the soft glass acts to close the opening blown therein thus again sealing oilthe lamp and automatically protecting the-fluorescent coating.

The relief and check valve device may be $itliated in the exhaust tube as described or it maybe situated at any desired point in the envelope.

After the lamp has become flattened under the action of the weight II it is allowed to cool and is then removed from the oven and may be completed at any time.

To complete the lamp the seal I3 is broken after which the tube 5 is connected to a pump to exhaust the lamp which then may be finally sealed and completed by basing and performing whatever other operations may be required to place the lamp in operating condition.

What I claim is: 1. A method of temporarily protecting from contamination an element within the envelope of a thermionic device comprising, introducing a. protective gaseous atmosphere into the envelope, forming a seal to keep the gas therein, subsequently performing added operations upon the device includin heating the device to a temperature sufllcient to break said seal, and cooling the device sumciently to effect a re-sealing of the broken seal.

2. A method of temporarily protecting from contamination an element within an envelope of a thermionic. device comprising introducing a protective gaseous atmosphere into the envelope, forming a seal to keep the gas'therein, applying heat to the envelope while sealed, said heat eifecting automatic venting of excessive pressure within the lamp caused by its rise in temperature.

through said seal and cooling the envelope to cause said seal to reseal the envelope after the pressure therein is reduced.

3. A method of temporarily protecting an internal fluorescent coating for a thermionic device during its manufacture comprising applying a coating of fluorescent material to the inner wall of its envelope, introducing an inert gaseous atmosphere into said envelope, forming a seal to keep the gas therein, performing additional operations thereon while thus sealed including heating the device to a temperature sufllcient to break said seal, and cooling the device sufficiently to eflect a re-sealing of the broken seal.

4. A method of temporarily protecting an internal fluorescent coating for a tubular thermionic device during its manufacture comprising applying a fluorescent coating to at least a portion of its inner wall, closing the ends of the tubular envelope to present an opening substantially smaller than the tube; introducing an inert gas at one end of said tube thereby flushing the air in the envelope out through the aperture at its other end, forming a seal at both ends of the tube thereby enclosin the gas therein, performing additional operations thereafter upon the device while thus sealed including heating the device to a temperature sufilclent to break said seal, and cooling the device sufllciently to effect a re-sealing of the broken seal.

5. A method of temporarily protecting a fluorescent coating upon the inner wall of the tubular envelope of a fluorescent lamp during its manufacture comprising applying the fluorescent coating to the open ended envelope. finishing the coating. fusing stem assemblies having an exhaust tube in at least one thereof to the respective ends of the tubular envelope. introducing an inert atmosphere into said'envelope through said exhaust tube, forming a seal on the outside end of said exhaust tube, subsequently performing additional operations u on the lamp while thus sealed including heat ng the lamp to a temperature suf-' iicient to break said seal, and cooling the lamp sumciently to eflect a re-sealing of the broken seal.

6. A method of temporarily protecting the fluorescent coating upon the inner wall of a tubular fluorescent lamp during its manufacture compris- 6 nnmmnnons crrm The following references are 01' record in the iiie oi this patent:

UNITED s'iwm's PATENTS Number Name Date 1,911,410 Valverde -1. May 30, 1933 2,160,081 Niclassen May 30, 1939 2,205,809 Breadner et a1. June 25, 1940- 2301174 Jenkins July 9, 1940 2,277,691 Curwen et a1 Mar. 31, 1942 2,299,720 Holman Oct. 20, 1942 OTHER REFERENCES Mobius-NeonLeucht Rohren, 1932, pages 26 and 27. (Copy in Div. 54.) 

